The relationship between severity of head injury and outcome was studied in 96 patients. Severity was assessed based on the level of coma and presence of mass lesion, hemiparesis, skull fracture, and pupil abnormality. Outcome was assessed using the Wechsler Adult Intelligence Scale, the Halstead-Reitan neuropsychological battery, and the Glasgow Outcome Scale. The relationship between assessment of severity of trauma and the outcome measurements was calculated by multiple regression analysis. Results indicate that coma grade and estimates of premorbid intelligence quotient (IQ) served best to predict IQ as assessed after the injury. The combination of coma grade, mass lesion, and skull fracture were important predictors of the Halstead Impairment Index. Coma grade and pupil abnormality predicted the Glasgow Outcome Scale. Low to moderate relationships were found between the predictor variables and the measurement of IQ and the Glasgow Outcome Scale; multiple regression coefficients were 0.63 and 0.61, respectively. The relationship between measurement of trauma severity and the Halstead Impairment Index was also low (R = 0.37).